Prevalence and antibiogram profiles of Escherichia coli O157:H7 isolates recovered from three selected dairy farms in the Eastern Cape Province, South Africa

Abstract

ObjectiveTo investigate the occurrence and antibiotics susceptibility of Escherichia coli (E. coli) O157:H7 isolates from raw milk, cattle udder, milking machines and worker's hand swabs from three selected commercial dairy farms in the Amathole District Municipality, Eastern Cape Province, South Africa. MethodsRaw milk samples were collected from bulk storage tanks and swab samples were collected from milking machines, cattle udders and worker's hands fortnightly over a six-month sampling regime between June and November 2014. A standard culture-based method was used for the enumeration and isolation of E. coli O157:H7, presumptive identification using sorbitol MacConkey agar (supplemented with cefixime (50 μg/L) and potassium tellurite (25 mg/L). A serological confirmation of the presumptive E. coli O157:H7 isolates was conducted using the O157 latex agglutination test kit. ResultsA total of 252 E. coli O157:H7 isolates were further subjected to PCR amplification of rfbEO157 and fliCH7 genes of which 27(11%) of the isolates were confirmed positive E. coli O157:H7. The percentage antibiotic resistance of the 27 E. coli O157:H7 isolates from the dairy farms revealed penicillin [23 (85%)], tetracycline [22 (81%)], erythromycin [19 (70%)], streptomycin [14 (52%)] and chloramphenicol [12 (45%)]. The highest resistances were penicillin [23 (85%)] and tetracycline [22 (81%)]. ConclusionsThese findings revealed that the dairy farms are potential reservoirs of E. coli O157:H7 serotype, and harbor antibiotic-resistant determinants, a concern to public and environmental health.